Relationship Between Isokinetic Muscle Strength of the Affected Lower Extremity and Walking Speed and Gait Asymmetry in Stroke Patients

• Main Authors: Ann-Lun Hsu, 許安倫
• Other Authors: Pei-Fang Tang
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/99593460082723080157

碩士 === 國立臺灣大學 === 物理治療學研究所 === 88 === The purposes of this study were: first, to evaluate muscle performance and the test-retest reliability of isokinetic muscle strength of bilateral lower extremities of stroke patients; next, to investigate the association between muscle strength of the affected lower extremity and gait performance, including walking speed and gait asymmetry, and to identify the primary predictors of gait performance; and last, to identify the most important impairments determining gait performance. Twenty-six first time-onset stroke patients (mean age = 54.2 ± 10.9 years, post-stroke time = 1-43 months), who were able to walk independently without any assistance or device, participated in the study. The impairments in motor function and sensation of the affected lower extremity were evaluated with the Fugl-Meyer Assessment. Spasticity of the ankle plantarflexors on affected lower extremity was examined using the modified Asworth Scale. A Cybex 6000 dynamometer was used to measure maximal isokinetic strength of the hip flexors, knee extensors and ankle plantarflexors of bilateral lower extremities at slow and faster angular velocities. Gait performance, including comfortable and fastest walking speed and temporal and spatial asymmetry, was evaluated with the GaitMatⅡsystem. Nine of the subjects also participated in the test-retest reliability study on isokinetic muscle strength testing. Results revealed that for both lower extremities, the muscle strength measures normalized to body weight were all significantly reliable. However, for the affected lower extremity, not all of the muscle strength measures normalized to the corresponding muscle strength on the unaffected side, namely the strength deficit measures, were significantly reliable. For the knee extensors and ankle plantarflexors on affected side, the isokinetic strengths generated at faster angular velocity were more reliable than those generated at slow angular velocity. But the hip flexor did not show such speed-related differences in the test-retest reliability of muscle strength measures. Among the different measurement methods, the normalized peak torque and total work were more reliable than normalized average power. The hip flexor and knee extensor strengths were more reliable than ankle plantarflexor strength. In general, muscle performance of the affected lower extremity, including normalized peak torque and total work, was smaller than that of the unaffected side. This indicated that muscle strengths of affected lower extremity were indeed impaired in stroke patients. Muscle strengths of all three investigated muscle groups of the affected lower extremity were significantly related to walking speed. The regression analysis revealed that the hip flexor and ankle plantarflexror strengths significantly predicted subjects’ comfortable walking speed (R2 = 0.40), whereas the knee extensor, hip flexor and ankle plantarflexror strengths significantly predicted subjects’ fastest walking speed (R2 = 0.62). Only the ankle plantarflexror strength on the affected side was significantly related to the temporal asymmetry in gait, and ankle plantarflexror and hip flexor strengths were the significant predictors of the temporal asymmetry in gait (R2 = 0.40). The ankle plantarflexror and knee extensor strengths were significantly related to the spatial asymmetry in gait and these two factors significantly predicted the spatial asymmetry in the comfortable and fastest walking speed conditions, respectively (R2 = 0.28 & 18). When all impairments, including strength, motor function and sensation of the affected lower extremity, and spasticity of the ankle plantarflexor, were considered together, the regression analysis revealed that the hip flexor strength, spasticity of the ankle plantarflexror and sensation significantly predicted subjects’ comfortable walking speed (R2 = 0.57), whereas the knee extensor strength, motor function, sensation and hip flexor strength of the affected lower extremity significantly predicted subjects’ fastest walking speed (R2 = 0.72). For the temporal asymmetry in gait, the spasticity of ankle plantarflexror, motor function and sensation of affected lower extremity were significant predictors (R2 = 0.76). For the spatial asymmetry in gait, the spasticity of ankle plantarflexror and knee extensor strength were significant predictors (R2 = 0.46). It was concluded that isokinetic muscle strength evaluation of the affected lower extremity in stroke patients, measured as normalized peak torque and total work, had good test-retest reliability. Muscles of the paretic lower extremity generated smaller voluntary strength than their counterparts of the unaffected lower extremity. Walking speed and gait asymmetry were differentially affected by the investigated impairments. The hip flexor and knee extensor muscle strengths of the affected lower extremity were the most important factors determining the comfortable and fastest walking speed, respectively, of hemiplegic patients. On the contrary, the spasticity and strength of ankle plantarflexors appeared to be critical factors predicting temporal and spatial asymmetry in hemiplegic gait. Therapeutic interventions that aim at improving walking speed of hemiplegic patients may need to place emphasis on hip flexor and knee extensor strengthening exercises, whereas those target at improving gait symmetry may need to apply therapies that can effectively reduce the spasticity or improve muscle strength of ankle plantarflexors.